Relating to breathing systems

ABSTRACT

Apparatus (10,226,326) for condensing water from respiratory gases, comprising a heat exchange component (20,234,334) having an inlet (22,228,328), an outlet (24,228,230) and a condensation chamber, the inlet and outlet (22,24,228,230,328,330) being connectable to a breathing system, such that respiratory gases are conveyed through the condensation chamber, in use, and a base unit (30,232,332) adapted to aid removal of heat from the walls of the heat exchange component (20,234,334), wherein the heat exchange component (20,234,334) is releasably engageable with the base unit (30,232,332), such that the heat exchange component (20,234,334) is replaceable.

This application is a continuation of U.S. patent application Ser. No.13/991,265, which is a national stage application under 35 U.S.C. § 371from PCT Application No. PCT/GB2011/052124, filed Nov. 1, 2011, whichclaims the priority benefit of Great Britain Application No. 1020496.4,filed Dec. 3, 2010, which are hereby incorporated by reference in theirentirety.

This invention relates to breathing systems, and in particular to themanagement of water vapour and water condensate in breathing systems.

In a healthy person, the function of breathing is entirely spontaneous.The brain senses a build-up of carbon dioxide in the blood andimmediately calls for more oxygen. This oxygen is taken into the body byspontaneous inspiration and carbon dioxide is removed in the passiveexhalation phase of respiration. A healthy person generates a certainamount of humidity, which is used in the lung to stop the build-up ofsecretions.

The ability to breathe spontaneously may be lost for a number ofreasons. Examples are as a result of surgical procedures(post-operatively), as a result of certain muscular disorders affectingthe lung, or as a result of sedation by a clinician. Patients thusaffected must be ventilated by mechanical means in order to achieveoxygenation and carbon dioxide removal.

When a patient is mechanically ventilated, it is essential that thehumidity of the air is maintained at a sufficiently high level, since alung with impaired function will be more susceptible to secretions. Thisis conventionally achieved using a heat-moisture exchanger (HME) or aheated water bath humidifier. An HME retains the moisture in an exhaledbreath and this moisture is sent back to the lung with the nextinspiratory phase. In a water bath system, the inspiratory gas is passedthrough a heated water chamber and picks up humidity prior to enteringthe lung.

As humid respiratory gases travel through a breathing system, either inthe inspiratory limb or the expiratory limb of a breathing circuit, acertain amount of water vapour will cool and start to condense, formingwater droplets, which will start to build up, causing so-called“rain-out”.

It is important to remove water condensate from the breathing system, sothat it does not occlude the respiratory air flow or drain back into thepatient's lungs thereby putting the patient at risk of drowning, or doesnot drain into the ventilator/anaesthetic equipment thus causing damage.If it is allowed to accumulate for a protracted period then due to itsnon-compressible nature the water will effectively block the breathingsystem.

The conventional arrangement for managing moisture in such a system isby the use of a device called a water trap. Such a device is generallylocated at the mid-point of the breathing system and positioned at thelowest point so that liquid will drain into it. Periodically, theaccumulated condensate is emptied and the water trap replaced. However,this arrangement is not entirely satisfactory because water condensatestill forms within the breathing system, and this water condensate mayinterfere with the operation of valves, sensors or ventilation machineryof the system. In particular, in conventional arrangements, it is commonfor water condensate to accumulate at the ventilator exhalation valve,for example. This can cause problems with flow measurement, resistanceto flow, false triggering of alarms, and indeed occlusion of tubes.

It is also known to attempt to dehumidify the respiratory gases within abreathing circuit, for example before the respiratory gases aredelivered back to the ventilator. One such arrangement is an exhalationbreathing tube with an enclosing wall that allows the passage of watervapour therethrough, but prevents the passage of respiratory gases.However, these exhalation breathing tubes are expensive to manufacture,and typically only remove a portion of the water vapour content from therespiratory gases. In addition, use of these exhalation breathing tubesresults in water vapour that has been exhaled from a patient enteringambient air, which is then inhaled by clinicians.

There has now been devised apparatus which overcomes or substantiallymitigates the above-mentioned and/or other disadvantages associated withthe prior art.

According to a first aspect of the invention, there is providedapparatus for condensing water from respiratory gases, comprising a heatexchange component having an inlet, an outlet and a condensationchamber, the inlet and outlet being connectable to a breathing system,such that respiratory gases are conveyed through the condensationchamber, in use, and a base unit adapted to aid removal of heat from thewalls of the heat exchange component, wherein the heat exchangecomponent is releasably engageable with the base unit, such that theheat exchange component is replaceable.

According to a further aspect of the invention, there is provided a heatexchange component for condensing water from respiratory gases having aninlet, an outlet and a condensation chamber, the inlet and outlet beingconnectable to a breathing system, such that respiratory gases areconveyed through the condensation chamber, in use, wherein the heatexchange component is releasably engageable with a base unit adapted toaid removal of heat from the walls of the heat exchange component.

According to a further aspect of the invention, there is provided a baseunit for use with a heat exchange component for condensing water fromrespiratory gases, the base unit being adapted to releasably engage theheat exchange component, and the base unit being adapted to aid removalof heat from the walls of the heat exchange component.

The apparatus according to the present invention is advantageousprincipally because the apparatus condenses water from respiratory gaseswithin a heat exchange component, which enables the water to be removedfrom the breathing system. The present invention therefore reduces therisk that water condensate will form in the breathing system that willinterfere with the operation of valves, sensors or ventilation machineryof the system.

Furthermore, the respiratory gases are conveyed through a heat exchangecomponent that is releasably engageable with the base unit, such thatthe heat exchange component is replaceable. This enables the base unitto be arranged not to come into contact with the respiratory gases orwater condensate, and hence enables the base unit to be a reusablecomponent, with the heat exchange component being a disposablecomponent. This is advantageous as it means the apparatus can be usedsafely and cost effectively with multiple patients by replacing the heatexchange component between patients. In addition, the present inventionis less expensive than arrangements in which the entire apparatus isdisposable.

Indeed, where the apparatus and/or base unit include means for activelycooling the respiratory gases conveyed through the condensation chamber,in use, for example by transferring heat from the walls of the heatexchange component, the present invention provides particular costbenefits. In particular, the heat transfer device, eg a Peltier device,is preferably provided in the base unit of the present invention, andhence may be reused. Furthermore, the heat exchange component of thepresent invention is preferably of simple construction, eg formed fromtwo moulded parts, and hence inexpensive to manufacture.

The apparatus according to the invention is adapted to condense waterfrom respiratory gases. Most preferably, the apparatus includes anarrangement for removing the water condensate from the breathing system.The apparatus is preferably therefore suitable for removing watercondensate from a breathing system, and preferably includes anarrangement for collecting the water condensate for removal.

The heat exchange component includes a condensation chamber, throughwhich respiratory gases are conveyed, in use. The condensation chamberis preferably adapted to promote heat transfer from the respiratorygases, to the walls of the condensation chamber, such that water iscondensed from the respiratory gases, within the condensation chamber,in use. In particular, the condensation chamber preferably has anincreased interior surface area relative to a single flow passagewayhaving a generally circular cross-section. In presently preferredembodiments, the condensation chamber has a major wall that issubstantially corrugated in form.

The condensation chamber may have a plurality of flow passageways, whichare each adapted to convey respiratory gases, in use. Thecross-sectional shape of the condensation chamber, or each flowpassageway of the condensation chamber, may be adapted to provide anincreased interior surface area relative to that provided by a circularcross-section. In some embodiments, the condensation chamber comprises aplurality of flow passageways, which each have an elongated, internalcross-sectional shape. For example, the ratio of the internal width ofthe flow passage to the internal depth of the flow passage may be atleast 1:2, at least 1:3, at least 1:7, or about 1:10 or more.

The base unit is adapted to aid removal of heat from the walls of theheat exchange component. The base unit is preferably arranged to reducethe temperature of the respiratory gas flow downstream of the inlet. Thebase unit is preferably adapted to cool the respiratory gases within thecondensation chamber. This may be achieved in a variety of ways. Inparticular, the base unit may include a cooler arranged to cool therespiratory gases actively. The cooler may be connectable to a powersupply, and may provide transfer of heat away from the condensationchamber, for example to another part of the apparatus and/or thesurroundings, eg via a heat sink. The base unit may include a surface ofreduced temperature, relative to ambient temperature. This surface ofreduced temperature may be adapted to reduce the temperature of the airsurrounding the heat exchange component, or may be adapted to contactexterior surface(s) of the heat exchange component.

The base unit may comprise a heat exchange medium arranged to transferheat energy away from the condensation chamber. The base unit maycomprise a thermoelectric member for cooling the respiratory gaseswithin the condensation chamber. The thermoelectric member may bearranged to provide thermal communication away from the condensationchamber, for example to another part of the apparatus and/or thesurroundings, eg via a heat sink. The thermoelectric member may beconnectable to a power source such that it is arranged to drive heattransfer away from the condensation chamber.

The thermoelectric member may comprise a Peltier device.

In presently preferred embodiments, the base unit comprises a heatexchange medium, eg a thermoelectric member, having a cold side and ahot side, the cold side being arranged for thermal contact with thecondensation chamber of the heat exchange component adapted to aidremoval of heat from the walls of first portion. As discussed in moredetail below, the base unit may also be arranged such that the hot sideis in thermal contact with a heater chamber of the heat exchangecomponent, downstream of the first portion, in order to heat therespiratory gases prior to those gases exiting the heat exchangecomponent.

Alternatively, or in addition, the apparatus may be adapted to promotetransfer of heat from the respiratory gases to the surroundings, ie toprovide passive cooling, for example by providing a condensation chamberwith an exterior of increased surface area, for a given volume, relativeto a single flow passageway of substantially circular cross-section. Thebase unit may be adapted to generate an air flow across externalsurface(s) of the heat exchange component. This air flow may increasethe rate of conduction of heat away from the external surface(s) of theheat exchange component by causing air to which heat from the thosesurfaces has been conducted, and hence air that is at a raisedtemperature relative to ambient air, to be continuously replaced withair at a lower temperature. The air flow generated by the base unit maybe ambient air, or may be at a reduced temperature relative to ambientair.

The flow of air, eg ambient air, across external surface(s) of the heatexchange component may be generated by an electric fan, which may behoused within the base unit. The fan may be adapted to generate a flowof air that flows over external surface(s) of the heat exchangecomponent, and is then dissipated into the surroundings. The air flowgenerated by the base unit may be blown across external surface(s) ofthe heat exchange component, or may alternatively be drawn acrossexternal surface(s) of the heat exchange component, by the base unit, egby the electric fan. Once the air flow has traveled across externalsurface(s) of the heat exchange component, the air flow may be directedaway from the user, in use. In one embodiment, the base unit is adaptedto draw a flow of air across external surface(s) of the heat exchangecomponent, which is located at the front of the apparatus relative tothe user, eg relative to the clinician, and the base unit is adapted todissipate this air flow into the surroundings at the rear of the baseunit.

The condensation chamber may also be adapted to promote heat transferfrom the walls of heat condensation chamber, to ambient air, in use. Inparticular, the condensation chamber may adapted for effectivecooperation with the base unit. For example, it is generally preferredthat the condensation chamber has an increased exterior surface arearelative to a single flow passageway having a generally circularcross-section. In presently preferred embodiments, the condensationchamber has a major wall that is substantially corrugated in form.

The condensation chamber may comprise a plurality of flow passageways,which are each adapted to convey respiratory gases, in use. Thecross-sectional shape of the condensation chamber, or each flowpassageway of the condensation chamber, may be adapted to provide anincreased exterior surface area relative to that provided by a circularcross-section. In some embodiments, the condensation chamber comprises aplurality of flow passageways, which each have an elongated, exteriorcross-sectional shape. For example, the ratio of the exterior width ofthe flow passage to the exterior depth of the flow passage may be atleast 1:2, at least 1:3, at least 1:7, or about 1:10 or more.

Where the base unit is adapted to generate a flow of air across externalsurface(s) of the heat exchange component, as described above, thecondensation chamber may have an increased exterior surface area that isexposed to that air flow, relative to a single flow passageway having agenerally circular cross-section. Hence, in addition to having anarrangement as described above to provide an increased exterior surfacearea, the condensation chamber may be arranged relative to the base unitto expose at least 50%, at least 60%, or at least 80% of its totalexterior surface area to the air flow generated by the base unit. Inthis embodiment, the condensation chamber may be arranged relative tothe base unit with the major exterior surfaces of its flow passageway(s)substantially aligned with the air flow generated by the base unit. Thecondensation chamber may comprises a plurality of flow passageways,which are separated from one another to define one or more exteriorpassageways through the heat exchange component. The condensationchamber may be arranged relative to the base unit such that the air flowfrom the base unit is conveyed through the one or more exteriorpassageways. The one or more exterior passageways may be substantiallyaligned with the direction of flow of air from the base unit.

Where the base unit is adapted to generate a flow of air across externalsurface(s) of the heat exchange component, the condensation chamber maycomprise a plurality of flow passageways, each generally planar in form,which are aligned adjacent and parallel to each other, and which areseparated from one another to define exterior flow passagestherebetween. When engaged with the base unit, each exterior passagewaymay be substantially aligned with the direction of flow of air from thebase unit.

The inlet and outlet of the heat exchange component preferably each havethe form of a conventional tubular connector for connection to othercomponents of breathing systems. In addition, however, the inlet and/oroutlet may include an arrangement for deflecting incoming and/oroutgoing respiratory gases transversely relative to the central axis ofthe port(s). This arrangement may comprise a baffle, which may bearranged adjacent to the exit of the port, and may be aligned with theport, such that air is deflected around the baffle, in use.

The arrangement for collecting the water condensate for removal ispreferably separate from the breathing system, such that watercondensing within the heat exchange component does not re-enter thebreathing system. Hence, the heat exchange component preferably has theinlet and the outlet formed in an upper portion of the component, forexample at the upper end, in order to prevent the flow of watercondensate into the connected breathing system.

The heat exchange component may itself be adapted to collect watercondensate for removal, for example by incorporating the inlet andoutlet into a valve arrangement that enables disconnection of the heatexchange component from the breathing system, without enabling escape ofrespiratory gases. In presently preferred embodiments, however, the heatexchange component is preferably adapted for connection to a separatearrangement for collecting the water condensate for removal.

The heat exchange component preferably includes a water condensateoutlet port, which is adapted to enable the removal of water condensatefrom the heat exchange component, and most preferably from the breathingsystem. The water condensate outlet port preferably allows the flow ofwater condensate out of the heat exchange component, without allowingthe flow of respiratory gases through the port. Most preferably, thewater condensate outlet port includes a float valve, which allows theflow of water condensate out of the heat exchange component when thelevel of water condensate within the heat exchange component is at orabove a threshold level.

The heat exchange component is connectable to a breathing system, suchthat respiratory gases are conveyed through the condensation chamber, inuse. Hence, according to a further aspect of the invention, there isprovided a breathing system comprising apparatus as described above.

The breathing system is preferably a breathing circuit, which willtypically include at least a ventilator or an anesthesia machine, and aninspiratory limb. However, the present invention is particularlyadvantageous for removing water from exhaled gases, and hence thebreathing circuit preferably also includes an expiratory limb, and theapparatus according to the invention is preferably connected within thebreathing circuit, such that it forms part of that limb. In particular,the expiratory limb preferably comprises at least two breathing tubes,with the heat exchange component connected between those breathingtubes, preferably at the lowest point of the expiratory limb.

The apparatus according to the invention may also include a device forheating the respiratory gases in the expiratory limb, which is disposedbetween the heat exchange component and the ventilator or anesthesiamachine. This device is preferably adapted to maintain the respiratorygases above their dew point, thereby enabling further condensation to bereduced or prevented. Alternatively, or in addition, the apparatus maybe adapted to heat the respiratory gases to a temperature above theirdew point before the gases exit the heat exchange component. Thisarrangement reduces the likelihood that any remaining vapour within therespiratory gases will condense out of the gas flow within anotherportion of the breathing system.

The heat exchange component is preferably a disposable component, whichis preferably formed of plastics material. The heat exchange componentpreferably forms a closed system, relative to the base unit, such thatthere is no contact between the base unit, or any air flow generated bythe base unit, and the respiratory gases of the breathing system.

The heat exchange component and the base unit preferably includeformations that cooperate to mount the heat exchange component relativeto the base unit. In particular, the heat exchange component may beslidably engaged with the base unit, which may be achieved by means ofcooperating rails and grooves. In presently preferred embodiments, theheat exchange component is engageable with the base unit from above. Inthis arrangement, the heat exchange component is retained by the actionof gravity. However, a fastening arrangement may be provided.

In presently preferred embodiments, the base unit includes a recess,such that the heat exchange component is mounted within the recess ofthe base unit. In any event, at least one major surface of the heatexchange component is preferably exposed to the surroundings.

Where the base unit includes a heat exchange medium for transferringheat away from the heat exchange component, eg the condensation chamber,and/or transferring heat to the heat exchange component, eg the heaterchamber, the base unit preferably includes one or more heat conductorsfor engaging the exterior surface of the heat exchange component. Inpresently preferred embodiments, the one or more heat conductors takethe form of projections or recesses for engaging corresponding, egmating, projections or recesses of the heat exchange component.

The base unit is preferably a re-usable component, and will typicallyinclude a connection to a power supply.

As described above, the heat exchange component preferably includes awater condensate outlet port, which is adapted to enable the removal ofwater condensate from the heat exchange component, and most preferablyfrom the breathing system. The apparatus according to the inventionpreferably includes an arrangement for collecting the water condensatefor removal, which is engageable with the water condensate outlet portof the heat exchange component. In particular, the apparatus accordingto the invention preferably includes a sump component that is removablyconnected to the water condensate outlet port of the heat exchangecomponent, where the sump component may have the form of a bag, avessel, or any other type of suitable container. Most preferably, theinterior of the sump component is expandable, such that the interior maybe substantially evacuated prior to use.

The sump component may be connected directly to the water condensateoutlet port, or may be connected via tubing for transporting the watercondensate. The apparatus preferably also includes an arrangement forclosing the water condensate outlet port when the sump component isremoved for emptying or disposal. This closure arrangement may take theform of a valve in the water condensate outlet port. In a preferredembodiment, the valve includes one or more duckbill valves, which aremaintained in an open configuration by the presence of the sumpcomponent in connection with the heat exchange component, and whichrevert to a closed configuration when the sump component is disconnectedfrom the heat exchange component. For example, the sump component may beadapted to cause the movement of resiliently movable, outwardlyextending arms of the valve on connection of the sump component to theheat exchange component. In a particularly preferred embodiment, thevalve includes two duckbill valves, which are coupled by a connectionmember, such that connection of the sump component to the heat exchangecomponent causes both duckbill valves to open

As described above, the apparatus may be adapted to heat the respiratorygases to a temperature above their dew point before the gases exit theheat exchange component. This arrangement reduces the likelihood thatany remaining vapour within the respiratory gases will condense out ofthe gas flow within another portion of the breathing system.

In this embodiment, the heat exchange component may comprise acondensation chamber and a heater chamber, the condensation and heaterchambers being arranged in flow series.

According to a further aspect of the invention, there is provided a baseunit for use with a replaceable heat exchange component for condensingwater from respiratory gases, the base unit being adapted to releasablyengage the heat exchange component, and the base unit comprising a heatexchange device having a cold side and a hot side, the cold side beingarranged for thermal contact with a first portion of the heat exchangecomponent and the hot side being arranged for thermal contact with asecond portion of the heat exchange component.

According to a further aspect of the invention, there is provided a heatexchange component for condensing water from respiratory gases, thecomponent having a condensation chamber portion having an inlet and aheater chamber portion having an outlet, the inlet and outlet beingconnectable to a breathing system, wherein the condensation chamberportion and the heater chamber portion are in fluid communication suchthat respiratory gases are conveyed from the inlet through condensationand heater chamber portions in use prior to passing through the outlet,wherein the heat exchange component is releasably engageable with a baseunit adapted to aid removal of heat from the condensation chamber and/oraid provision of heat energy to the heater chamber portion.

The apparatus may therefore comprise a condenser including thecondensation chamber and a heater including the heater chamber, theheater being downstream of the condenser for increasing the temperatureof the respiratory gas flow prior to the outlet.

The heater may be adapted so as to raise the temperature of therespiratory gas flow to a temperature greater than its dew point priorto passing through the outlet. The heater may be adapted to heat therespiratory gases passively, but the heater is preferably adapted toheat the respiratory gases actively. The heater may be adapted togenerate heat, which is transferred to the respiratory gas flow. Theheater may produce a substantially constant amount of heat, such thatthere is no control of the heater, eg the heater is provided with aconstant power supply. Alternatively, the apparatus may include acontroller for the heater, for example to provide the respiratory gasflow with a predetermined temperature, or range of temperatures, at theoutlet. This controller may control the power supplied to the heater,and may utilise one or more sensors for enabling feedback control.

The condenser may be arranged to reduce the temperature of therespiratory gas flow downstream of the inlet, and upstream of theheater. The condenser may be adapted to cool the respiratory gaseswithin the condensation chamber. The condenser may be adapted to promotetransfer of heat from the respiratory gases to the surroundings, ie toprovide passive cooling, for example by providing a condensation chamberwith an exterior of increased surface area, for a given volume, relativeto a single flow passageway of substantially circular cross-section.Alternatively, or in addition, the condenser may include a coolerarranged to cool the respiratory gases actively. The cooler may beconnectable to a power supply, and may provide transfer of heat from thecondenser to the heater and/or a heat sink.

The temperature of the gas passing through the outlet may be greaterthan the temperature of the gas in the condenser. The condenser may bearranged to reduce the temperature of the respiratory gas flow to atemperature less than or equal to its dew point, and the heater may beadapted so as to raise the temperature of the respiratory gas flow to atemperature greater than its dew point.

The condensation chamber and the heater chamber may comprise differentregions of a common chamber or enclosure. The heat exchange componentmay form a common housing for the condensation chamber and the heaterchamber. The condensation chamber and the heater chamber may comprise aplurality of heat conducting walls.

The base unit may comprise a heat exchange medium arranged to transferheat energy from the condenser to the heater. The heater and condensermay share a common heat exchange medium. Such an arrangement isadvantageous in that the energy consumed by the apparatus in use isreduced by re-heating the gas flow using the heat energy removed fromthe flow by the condenser.

The base unit may comprise a thermoelectric member. The thermoelectricmember may be arranged to provide thermal communication between thecondenser and heater. The thermoelectric member may be connectable to apower source such that it is arranged to drive heat transfer from thecondenser to the heater. The condenser may comprise a cold side of thethermoelectric member and the heater may comprise a hot side of thethermoelectric member.

The thermoelectric member may comprise a Peltier device.

Either of the condensation and heater chambers may comprise heatexchange members arranged to protrude into the path of the flow throughthe apparatus. The heat exchange members may comprise one or moreupstanding walls arranged to define one or more flow passages throughthe condensation chamber and/or the heater chamber. The upstanding wallsmay take the form of baffles which may be arranged so as to define atortuous flow path through the condensation chamber and/or the heaterchamber. In one embodiment, the first and second portions are defined bya chamber with at least one wall being formed with inwardly projectingmembers, for example at least one wall may include corrugated portions.

One of the condensation chamber and the heater chamber may have a volumewhich is larger than that of other. A length, width or depth dimensionof one of the chambers may be greater than that of the other chamber.Accordingly the time taken for the flow to pass through one of thechambers may be greater than the time taken for the flow to pass throughthe other chamber. One of the chambers may have a heat exchange surfacearea exposed to the flow there-through which is greater than the heatexchange surface area of the other chamber. Alternatively, the volume,dimensions and/or flow period may be equal for the chambers.

Even where the base unit comprises a heat exchange medium orthermoelectric member for transferring heat from the condenser to theheater, the apparatus may produce excess heat. The apparatus may includea heat sink for removing excess heat from the apparatus. The heat sinkmay be external of any condenser and/or heater chamber of the apparatus,and is preferably formed on the base unit. The heat sink may comprise aplurality of heat exchange elements, which may be exposed to ambientair. The heat sink may comprise a fan arranged to create a flow ofambient air over the heat exchange elements. The heat sink may bearranged to dissipate heat energy from the system to ambient air. Any ofthe preferable features described above in relation to any one aspect ofthe invention may be applied to any further aspect of the inventionwherever practicable.

Preferred embodiments of the invention will now be described in greaterdetail, by way of illustration only, with reference to the accompanyingdrawings, in which;

FIG. 1 is a front view of a first embodiment of apparatus according tothe invention;

FIG. 2 is a plan view of the apparatus of FIG. 1;

FIG. 3 is a cross sectional view of the first embodiment along lineIII-III in FIG. 1;

FIG. 4 is a cross sectional view of the first embodiment along the lineIV-IV in FIG. 1;

FIG. 5 is a plan view of a fan unit, which forms part of the firstembodiment;

FIG. 6 is a front view of the fan unit;

FIG. 7 is a rear view of the fan unit;

FIG. 8 is a side view of the fan unit;

FIG. 9 is a front view of the radiator component, which forms part ofthe apparatus according to the invention;

FIG. 10 is a side view of the radiator component;

FIG. 11 is a cross sectional view of the radiator component along theline XI-XI in FIG. 10;

FIG. 12 is a schematic diagram of a respiratory circuit including thefirst embodiment;

FIG. 13 is a schematic, cross sectional view of collection apparatus foruse with the apparatus according to the invention;

FIG. 14 is a schematic, cross sectional view of alternative collectionapparatus for use with the apparatus according to the invention;

FIG. 15 is a three-dimensional view from the front of a secondembodiment of apparatus according to the invention;

FIG. 16 is a three-dimensional view from the rear of the secondembodiment;

FIG. 17 is an underside view of the second embodiment;

FIG. 18 is a side view of the second embodiment;

FIG. 19 is a plan view of the second embodiment;

FIG. 20 is an underside view of the second embodiment with the cartridgeremoved;

FIG. 21 is a three-dimensional view from the front of a third embodimentof apparatus according to the invention;

FIG. 22 is a three-dimensional view from the front of the base unit ofthe apparatus of FIG. 21;

FIG. 23 is a three-dimensional view from above the cartridge of theapparatus of FIG. 21; and

FIG. 24 is a three-dimensional view from below the cartridge of theapparatus of FIG. 21.

FIGS. 1 to 4 each show a first embodiment of apparatus according to theinvention, which is generally designated 10. The apparatus 10 comprisesa radiator component 20 and a fan unit 30. The radiator component 20 isa replaceable and disposable component, which is adapted to form part ofan exhalation limb of a respiratory circuit, as described in more detailbelow. The fan unit 30, however, is a reusable electrical component,with which the radiator component 20 is releasably engaged, in use.

The radiator component 20 is shown engaged with the fan unit 30 in FIGS.1 to 4, as well as in isolation in FIGS. 9 to 11. The radiator component20 has an upper part that comprises an air inlet port 22 and an airoutlet port 24 at its upper end, each having downwardly-extending,flared flow passages that are fixed to a peripheral flange at the upperend of an intermediate part of the radiator component 20. The air inletport 22 and the air outlet port 24 are 22 mm tubular connectors, whichare adapted to connect to conventional breathing tubes of an exhalationlimb, in use. In addition, as shown in FIGS. 2 and 11, each of theflared flow passages extending downwardly from the ports 22,24 includesa circular baffle 23, which is generally planar in form, and disposedco-axially in relation to the associated port 22,24 and approximatelymid-way down the flared flow passage. Each baffle 23 has a diameter thatis slightly less than the diameter of the associated port 22,24, andacts to deflect incoming or outgoing respiratory gases transversely,such that the gas flow through the radiator component is more uniformacross its width.

The intermediate part of the radiator component 20 has a peripheralflange at its upper end, which defines an opening that is in fluidcommunication with the air inlet port 22 and the air outlet port 24. Atits lower end, the radiator component 20 has a peripheral flange thatdefines an opening in fluid communication with a lower part of theradiator component 20, which is discussed in more detail below.

Between the upper and lower flanges, the intermediate part of theradiator component 20 has a plurality of adjacent, but separate, flowpassageways 28, which provide fluid communication between the upper andlower parts of the radiator component 20. Each flow passageway 28 isdefined by an enclosing wall, which has an exterior surface that is incontact with ambient air.

Each flow passageway 28 extends vertically, and has a horizontalcross-sectional shape that is significantly elongated. In particular,the width of each flow passageway 28 (see FIG. 1) is of the order of 10times less than the depth of each flow passageway 28 (see FIG. 3), suchthat each flow passageway 28 has the form of a generally planer,radiator fin that conveys respiratory gases, in use.

The flow passageways 28 of the radiator component 20 are orientatedgenerally parallel to each other, with a regular separation between theenclosing walls of the flow passageways 28 that is approximately equalto the width of each flow passageway. The enclosing walls of adjacentflow passageways 28 are also joined by horizontal supporting webs 25,which are arranged in five rows, regularly spaced over the height of theflow passageways 28.

The arrangement of the flow passageways 28 and the supporting webs 25 isintended to maximize the exterior surface area of the enclosing wallsthat is in contact with the surrounding air. In addition, the flowpassageways 28 and the supporting webs 25 are all orientated parallel tothe direction of flow of air from the fan unit 30, as discussed in moredetail below, such that air from the fan unit 30 flows through exteriorpassageways defined between the enclosing walls and the supporting webs25.

The form of the flow passageways 28 is intended to optimize the internalsurface area of the enclosing walls, to which heat from the respiratorygases is conducted. In addition, the arrangement of flow passageways 28relative to the fan unit 30 is intended to optimize the external surfacearea of the enclosing walls that is subject to the air flow from the fanunit 30. This air flow from the fan unit 30 increases the rate ofconduction of heat away from the enclosing walls by causing air to whichheat from the enclosing walls has been conducted, and hence air that isat a raised temperature relative to ambient air, to be continuouslyreplaced with ambient air at a lower temperature.

As shown clearly in FIG. 2, the radiator component 20 is adapted to beaccommodated within a front portion 52 of the fan unit 30. Inparticular, the radiator component 20 comprises laterally opposed rails29, which extend along a central, longitudinal axis of each side wall ofthe radiator component 20. The rails 29 are adapted to be slidablyengaged with corresponding vertical grooves 32 in the front portion 52of the fan unit 30, as discussed in more detail below.

The lower part of the radiator component 20 comprises a generally planerbase, with an upstanding, peripheral skirt having an outwardlyprojecting flange at its upper end that is fixed to the flange at thelower end of the intermediate part of the radiator component 20. Thelower part of the radiator component 20 therefore defines a chamber 40disposed at the lower end of the flow passageways 28 of the radiatorcomponent 20, which acts as a sump for collecting water that condensesfrom the respiratory gases flowing through the radiator component 20,and flows down the flow passageways 28 under the influence of gravity.

The lower part of the radiator component 20 also includes a condensateoutlet port 26, which extends from the external surface of the lowerwall of the radiator component 20. The base of the radiator component 20includes a central aperture 42, which enables condensate to exit theradiator component 20 via the condensate outlet port 26. The condensateoutlet port 26 is therefore adapted to connect to suitable collectionapparatus. In this embodiment, the condensate outlet port 26 has theform of a tubular connector.

In addition, the lower part of the radiator component 20 includes asimple float valve arrangement, which comprises a top-hat shaped sealingmember 27 a, which sits over the central aperture 42 in the base of theradiator component 20, and a generally rectangular, planar float member27 b extending outwardly therefrom.

The float-valve arrangement is adapted to allow condensate to flowthrough the central aperture 42, into the condensate outlet port 26,when the level of condensate within the lower part of the radiatorcomponent 20 is above a threshold level. In particular, when the levelof condensate within the lower part of the radiator component 20 isabove a particular level, the float member 27 b and the sealing member27 a will be raised from the base of the radiator component 20 to asufficient extent that condensate is able to flow through the centralaperture 32, into the condensate outlet port 26. When the level ofcondensate within the lower part of the radiator component 20 falls backbelow the threshold level, the sealing member will be re-engaged withthe base of the radiator component 20, and flow of condensate throughthe central aperture 42, into the condensate outlet port 26, will beprevented once again.

The fan unit 30 is shown with the radiator component 20 installed inFIGS. 1 to 4, as well as in isolation in FIGS. 5 to 8. The fan unit 30comprises a housing having a rear portion 50 for accommodating a fan,and a front portion 52 for receiving the radiator component 20. Thehousing is formed in plastics material, and includes a cylindricalsleeve 36 within which a fan is mounted. The fan is not shown in theFigures, but would consist of a generally conventional electric fan,with a suitable electrical connection. In addition, the housing includesan integrally formed clip 54 on its rear surface, which is adapted tomount the fan unit 30 to a suitable rail, such as the rail of aventilator machine.

The rear portion 50 of the fan unit 30 has a wall that surrounds thefan, but includes air inlet and air outlet arrangements 38,39 in itsfront and rear walls, respectively.

The air inlet arrangement 38 in the front wall of the rear portion 50 ofthe fan unit 30 comprises a generally rectangular opening, with aplurality of cross-members extending across the opening. Thecross-members extend horizontally across the opening, and definegenerally horizontal outlet apertures that have a maximum height in acentral, vertical region of the opening, and a gradually decreasingheight towards each side. This arrangement results in a greater flow ofair through a central, vertical region of the front wall of the rearportion 50 of the fan unit 30, and is adapted to provide a generallyuniform flow of air through the radiator component 20.

The air outlet arrangement 39 in the rear wall of the rear portion 50 ofthe fan unit 30 comprises a generally circular opening, with a pluralityof cross-members extending across the opening. The cross-members extendhorizontally across the opening, and are generally planar members thatare orientated at an angle to the rear wall, but generally parallel toeach other, such that air blown through the opening is deflecteddownwardly relative to the fan unit 30.

The fan is adapted to draw air into the rear portion 50 of the fan unit30 through the air inlet arrangement 38 described above, and expel thatair through the air outlet arrangement 39 described above. Inparticular, the fan is arranged to draw air generally horizontallythrough the radiator component 20 and the air inlet arrangement 38, andexpel that air from the fan unit 30 through the air outlet arrangement39.

The front portion 52 of the fan unit 30 comprises a pair of opposingarms 56 that, together with the front wall of the rear portion 50 of thefan unit 30, define an enclosure for accommodating the radiatorcomponent 20.

As discussed above, the radiator component 20 comprises laterallyopposed rails 29, which extend along a central, longitudinal axis ofeach side wall of the radiator component 20. The rails 29 are adapted tobe slidably engaged with corresponding vertical grooves 32 in the frontportion 52 of the fan unit 30. These vertical grooves 32 are formedapproximately mid-way along the interior surface of each arm of the fanunit 30. This arrangement enables the radiator component 20 to beslidably engaged with the front portion 52 of the fan unit 30, fromabove.

The fan unit 30 also includes a ledge 34 at the lower end of frontportion 52 of the fan unit 30. This ledge 34 projects from the lower endof the pair of opposing arms 56 of the fan unit 30, as well as the frontwall of the rear portion 50 of the fan unit 30, and is continuous inform. The lower part of the radiator component 20 has a peripheralflange that projects outwardly from the lower part of the radiatorcomponent 20, as described above, which rests upon the ledge 34 when theradiator component 20 is fully engaged with the fan unit 30. Thevertical grooves 32 and the ledge 34 of the front portion 52 of the fanunit 30 therefore cooperate with the rails 29 and the lower flange ofthe radiator component 20 to retain the radiator component 20 within thefront portion 52 of the fan unit 30, but enable removal, andreplacement, of the radiator component 20 by slidable disengagement andengagement of the radiator component with the fan unit 30 from above.

Once installed in the fan unit 30, the radiator component 20 has a fixedorientation relative to the fan unit 30 during operation of theapparatus. In particular, the radiator component 20 is arranged suchthat the flow passageways 28 of the radiator component 20, and theexterior flow passageways 28 defined between the flow passageways 28 andthe supporting webs of the radiator component 20, are aligned with thedirection of air flow from the fan unit 30. The increased air flow froma central, vertical region of the air outlet arrangement 38 of the fanunit 30 counteracts the spread of air flow that occurs, in use,following exit from the air outlet arrangement 38, such that the airflow through the radiator component 20 is generally uniform across itswidth.

The fan unit 30 is a reusable component, which is mounted to a rail ofthe respiratory apparatus providing ventilation of the patient, andconnected to an appropriate power supply. The radiator component 20 is asingle-use, disposable component, which is formed of plastics material.In use, the radiator component 20 forms part of a breathing circuit, andthe radiator component 20 is engaged with the fan unit 30. Therespiratory gases flowing through the radiator component 20 are cooled,which causes condensate to form and collect within the radiatorcomponent 20, and this condensate is removed from the breathing circuitthrough the condensate outlet port 26 using suitable collectionapparatus. This use of the apparatus according to the invention isdescribed in more detail below.

FIG. 12 is a schematic diagram of an example breathing circuit includingthe apparatus 10 according to the invention. The breathing circuitcomprises a ventilator 50, an inspiratory limb for deliveringrespiratory gases to a patient 80 for inhalation, and an expiratory limbfor transporting exhaled respiratory gases back to the ventilator. Theinspiratory limb comprises two breathing tubes 74,76, and a humidifier60 between the two breathing tubes 74,76 for humidifying the respiratorygases before inhalation by the patient 80. The breathing tube 76disposed between the humidifier 60 and the patient 80 is typicallyheated, in order to maintain the temperature and humidity of therespiratory gases at a desired level for inhalation.

The expiratory limb comprises two breathing tubes 70,72, and thedehumidifying apparatus 10 of the invention connected between the twobreathing tubes 70,72 for removing water vapour from the exhaledrespiratory gases before those respiratory gases are returned to theventilator 50. Removal of water vapour from the exhaled respiratorygases in the expiratory limb of a breathing circuit reduces the risk ofdamage being caused to the ventilator by the water vapour, and alsoreduces the amount of condensation that occurs within the breathingtubes 70,72 of the expiratory limb, which may restrict or occlude theflow passageways of the breathing tubes 70,72.

In use, when the patient 80 exhales, expired air is carried along afirst breathing tube 70 and enters the radiator component 20 of thedehumidifying apparatus 10 via the air inlet port 22. The expired air isdeflected transversely by the baffle 23 in the flared passageway, andenters the flow passageways 28 that extend from the lower end of theflared passageway, on one side of the radiator component 20. The expiredair flows down the flow passageways 28, to the chamber 40 in the lowerpart of the radiator component 20, and then flows up the flowpassageways 28 on the other side of the radiator component 20, whichlead to the air outlet port 24.

The provision of a plurality of flow passageways 28 within the radiatorcomponent 20, which each have a width that is significantly less thanits length or depth, means that the internal surface area of the wallsof the flow passageways 28, to which heat from the respiratory gases isconducted, is significantly increased relative to a conventionalbreathing tube, or a water trap chamber. The rate at which heat isconducted through the walls of the radiator component 20, to the ambientair, is therefore significantly increased.

In addition, the fan unit 30 causes air to flow through the exteriorpassageways defined between the enclosing walls of the flow passageways28, and the supporting webs, of the radiator component 20. This air flowfrom the fan unit 30 increases the rate of conduction of heat away fromthe enclosing walls of the flow passageways 28 by causing air to whichheat from the enclosing walls has been conducted, and hence air that isat a raised temperature relative to ambient air, to be continuouslyreplaced with ambient air at a lower temperature.

The dehumidifying apparatus 10 therefore causes the respiratory gasesflowing through the radiator component 20 to be cooled significantly,such that water vapour condenses into water within the radiatorcomponent 20, during use. The water condensate within the radiatorcomponent 20 flows down the flow passageways 28, into the chamber 40 inthe lower part of the radiator component 20, where it collects. Once thelevel of condensate within the lower part of the radiator component 20is above a threshold level, the float-valve arrangement of the radiatorcomponent 20 allows condensate to flow through the central aperture,into the condensate outlet port 26. The water condensate then flows intosuitable collection apparatus.

One such collection arrangement is shown schematically in FIG. 13. Inthis arrangement, the base of the radiator component 20 includes anenlarged central aperture 142, and an upstanding spout 144 extends fromthe central aperture 142 that is closed by the sealing member 27 a whenthe level of water is below the threshold level. Within the centralaperture 142 and the condensate outlet port 26, the radiator component20 is further provided with a valve arrangement that is opened byengagement of a collection vessel 110 with the condensate outlet port26, and closed by removal of the collection vessel 110.

The valve arrangement comprises an upper duckbill valve 120, a lowerduckbill valve 130, and a central connection member 140. The lowerduckbill valve 130 includes an outwardly projecting flange 132 that isadapted to be engaged by the upper end of the collection vessel 110, onconnection with the condensate outlet port 26, such that the outwardlyprojecting flange 132 of the lower duckbill valve 130 is urged upwardly.This action causes the lower duckbill valve 130 to be opened. Inaddition, this action causes the central connection member 140 to bemoved upwardly, causing the upper duckbill valve 120 to open. The openconfigurations of the upper and lower duckbill valves 120, 130 define anoutlet passageway 142 from the interior of the upstanding spout 144,into the condensate outlet port 26 and the collection vessel 110.

In this embodiment, the collection vessel 110 is adapted to connect tothe condensate outlet port 26 by means of a bayonet connection. Inaddition, the collection vessel 110 has a bellows structure, such thatthe collection vessel 110 may be substantially evacuated before use, andexpand during use as water condensate collects in the vessel 110.

An alternative collection arrangement is shown schematically in FIG. 14.In this arrangement, the base of the radiator component 20 againincludes an enlarged central aperture 152, and an upstanding spout 154extending from the central aperture 152 that is closed by the sealingmember 27 a when the level of water is below the threshold level. Inthis arrangement, however, the condensate outlet port 26 has a reduceddiameter, and is adapted to be connected to one end of a length of smallbore tubing 160 that is conventionally using to deliver fluids inmedical apparatus. The small bore tubing 160 is connected at its otherend to a collection bag 170, within which water condensate is collected.A tube clamp 180 is provided at each end of the small bore tubing 160,which enables the tubing 160 to be closed when replacing the collectionbag 170. Otherwise, the small bore tubing 160 remains open during use. Aduckbill valve 162 is also provided within the end of the small boretubing 160 that is connected to the collection bag 170.

A further development of this invention consists of the inclusion of athermoelectric element, and specifically a Peltier device, in the baseunit of the apparatus, and the provision of both a condensation chamberand a downstream heater chamber in the heat exchange module. In thisarrangement, the cold side of the thermoelectric element cools therespiratory gases in the condensation chamber, and the hot side of thethermoelectric element warms the respiratory gases in the downstreamheater chamber. This heating of the respiratory gases before exiting theheat exchange module reduces the likelihood that any remaining vapourwithin the gas flow will condense out of the gas flow within anotherportion of the breathing system.

A second embodiment of apparatus according to the invention is describedin detail below, with reference to FIGS. 15 to 20.

FIGS. 15 to 20 each show dehumidification apparatus according to theinvention, which is generally designated 226. The apparatus comprises abase unit 232 and a removable/replaceable cartridge 234. The cartridge234 may otherwise be considered to constitute a gas flow vessel or flowchamber.

The cartridge 234 generally comprises a thin-walled, hollow membershaped to define an internal gas-filled void. The cartridge 234 providesa gas-tight chamber with the exception of the ports 228, 230 and 236.The ports 228 and 230 provide respective inlet and outlet ports for theflow of respiratory gas into and from the cartridge 234 in use. The port236 is a liquid drainage port, the details of which will be describedbelow.

The ports 228 and 230 are provided in a common outer wall 238 of thecartridge 234, which wall in use is typically arranged to provide anupper, or upwardly facing, wall of the cartridge 234. An opposing, lowerwall 239 is provided, which constitutes the base of the cartridge 234 inan in-use orientation as shown in FIGS. 2 and 3. The ports 228 and 230are provided with respective upstanding connector formations 240, whicheach take the form of an annular wall depending from the wall 238. Theconnectors 240 are of conventional size to closely and securely fit withthe ends of breathing tubes 222 and 224 as shown in FIG. 15. Whenconnected in this manner, the internal chamber of the cartridge 234 issealed from ambient air and/or any external devices such that theinterior of the cartridge 234 forms a part of the closed flow path ofthe respiratory system shown in FIG. 15.

The cartridge 234 is preferably formed of a suitably rigid plasticmaterial, for example by injection moulding.

The cartridge 234 is generally rectangular in plan and has asubstantially continuous front wall 242, which faces away from the baseunit 232 when the cartridge is mounted thereon for use.

The opposing (rear) wall 244 of the cartridge, which faces the base unit232 has a series of longitudinal slots or recesses therein. In thisregard the wall structure of the cartridge 234 is shaped to provide aplurality of wall projections 248 which protrude from the rear wall 244into the internal volume of the cartridge 234. Those projections 248thus reduce or ‘eat into’ the internal volume of the cartridge 234. Thewall projections 248 can be seen from above in FIG. 19 through the ports228, 230.

The flow channels thus present a large internal wall surface area to theflow passing through the cartridge so as to increase the area availablefor heat transfer to/from the flow in use.

Turning now to FIGS. 16 and 18, there are shown further details of thebase unit 232 which comprises a heat-dissipating structure comprising aseries of generally planar fins 252 depending from a support plate 254.The fins 252 are generally upstanding from the support plate, typicallyperpendicularly thereto. The fins 252 are spaced along the plate 254 andgenerally parallel in alignment such that each fin 252 is spaced from anadjacent fin 252 by an air-gap.

Each fin 252 is supported only along one edge by the plate 254 such thatthe further sides of the heat-dissipating structure, comprising of thealigned edges of the fins, are open. The fins and support plate areformed of metal as a unitary structure and may be unitarily formed.

A fan unit 256 is mounted on the rear side of the heat dissipatingstructure. The rear side is the open side of the structure whichopposes, or faces away from, the support plate 254. The fan unit 256comprises a fan 258 arranged for rotation within a fan housing 260, bywhich the fan unit 256 is attached to the heat dissipating structure.The fan unit 256 is electrically powered to drive the fan in rotation ina direction which draws ambient air through the fins and expels air tothe surroundings, typically in a direction away from the apparatus 226.In the orientation shown in FIG. 16, the fan 256 rotates anti-clockwise.

Turning now to FIGS. 17 and 20, there are shown respective views of thebase unit 232 with and without the cartridge 234 attached. A heattransfer structure 262 is provided between the heat dissipatingstructure and the cartridge 234. The heat transfer structure dependsfrom the support plate 254 in a direction facing away from the fan unit256.

The heat transfer structure 262 comprises a heat transfer element orheat pump 264, which is arranged between thermal conductors 266 and 268.In this embodiment, the heat pump 264 is a thermoelectricheating/cooling device, which takes the form of a Peltier device. Such adevice may otherwise be described as a solid-state active heat pump. ThePeltier device has opposing major faces which are plate-like conductorsand a plurality of thermoelectric elements there-between (not shown),which are arranged electrically in series but thermally in parallelbetween the opposing plate conductors. Accordingly the supply ofelectric power to the device drives a temperature difference between theconductor plates such that a first plate conductor comprises a cold sideof the device and the opposing conductor comprises a hot side of thedevice.

The cold side of the Peltier device 264 is connected to the conductorarrangement 266. This conductor arrangement comprises a plurality ofprojections 270 depending away from the Peltier device. The projections270 are spaced in a series or configuration which corresponds to therecesses 246 in the rear wall of the cartridge. The projections 270 areelongate in form and upstanding akin to fins or finger-like formationswhich are shaped to form a close fit with the wall projections of thecartridge 234 and thereby form a good thermal contact therewith. Theprojections 270 depend from a generally planar backing portion whichforms a thermal contact over the area of the cold side of the Peltierdevice for heat transfer therewith.

The hot side of the Peltier device 264 is connected to conductorformation 268, which comprises a relatively thin walled or planar body272 which is sandwiched between the hot side of the Peltier device 264and the back/support plate 254 of the heat dissipating structure.Towards an edge of the body 272 (i.e. towards the right hand edge asshown in FIG. 20), there are provided further upstanding projections274. The projections 274 project outwardly from the body 272 in the samedirection as the projections 270. The projections 274 in this embodimentare shaped and spaced in a manner which corresponds to that of theprojections 274. Hence the projection 270 and 274 are substantially thesame shape.

However, it can be seen that there are fewer of the projections 274 thanthere are of projections 270. In this embodiment, the ratio between theprojections 270 and 274 is 3:1, such that there are six ‘cold’projections 270 and only two ‘hot’ projections 274. However differentratios and/or numbers of projections 270,274 may be provided asnecessary. The combined array of the projections 270 and 274 is arrangedfor insertion into the recesses 246 in the cartridge, such that some ofthe recesses are filled by the projections 270 and other recesses arefilled by projections 274. It is notable that the projections 270 aregrouped, as are the projections 274 such that those different types ofprojections are not interspersed.

The cartridge 234 is mounted for use to the base unit 232 by aligningthe projections 270, 274 with the recesses in the rear wall of thecartridge 234 and then moving the cartridge 234 rearwardly (in thedirection of arrow A in FIGS. 17 and 18) such that the projections slotinto the recesses. In alternative embodiments, the cartridge 234 couldbe slid over the projections 270,274 in the longitudinal direction. Ineither embodiment, the cartridge 234 and/or projections 270,274 could beprovided with one alignment grooves or ridges to ensure a close/tightfitment between the cartridge 234 and base unit 232.

In readiness for use, the ports 228 and 230 are connected to therespective tubes 70 and 72 in the respiratory system as shown in FIG.12. The base unit 232 is also connected to a power supply, whichtypically comprises a connection to a mains power supply by a suitablelead (not shown), such that electrical power is supplied to the Peltierdevice 264 and fan unit 256. The supply of power to the Peltier device264 drives a temperature difference between the opposing sides of thedevice by thermoelectric effect, thereby cooling the projections 270,whilst heating projections 274.

Thus, in use, when a cartridge 234 is located on the device such that itis in thermal conductive contact with the projections 270,274, a firstplurality of the internal wall portions 248 are cooled by projections270, whist a second plurality of wall portions of the cartridge areheated by projections 274. This results in the internal cavity of thecartridge in use having a cooled region upstream of a heated region.Thus the gas entering the cartridge 234 at the inlet port 228 is firstcooled by the walls of the cartridge 234, promoting condensation of thevapor within the expired gas flow from the patient. In this regard, thegas flow is typically cooled to at or below its due point, such thatcondensation readily occurs on the internal walls of the cartridge.

Although the cartridge is formed of a generally thin-walled structure,it is noted that the rear wall 244 and/or wall projections 248 whichdefine the recesses in the cartridge are particularly thin walled andmay have a wall thickness that is lower than that of the remainder ofthe cartridge. This is to ensure a low impedance to heat transfer fromthe gas flow to/from the base unit projections 270, 274.

Once the gas flow passes the final cooled internal wall projection inthe cartridge, the gas then enters heated flow passages defined by thedownstream internal cartridge walls that are heated by the base unitheater projections 274. Thus heat energy removed from the gas flow bythe Peltier device 264 is conducted back to the downstream walls of thecartridge via conductor 272 and projections 274 so as to reheat the gasflow to above its dew point before the gas exits the cartridge via theoutlet port.

The multiple flow channels caused by the internal baffles within thecartridge 234 provides a large surface area for extracting heat energyfrom the gas flow. Also the channels within the cartridge 234 define aflow path for the gas such that the heated portion of the cartridgechamber is arranged downstream in flow series from the cooled cartridgeportion. This helps to ensure that heat is not transferred to the cooledsection by either conduction or else convection.

It has been found that the amount of heat generated by the Peltierdevice is greater than the amount of heat energy needed to reheat thegas flow to above its dew point. Accordingly the connection between thebody 272 on the hot side of the Peltier device and the heat dissipatingstructure 232 allows excess heat to be lost to the ambient air. Thus theheat dissipating structure acts as a heat sink for the system. The rateof heat loss to ambient air is increased by the airflow caused by fan58.

It is a notable advantage that the interior of the cartridge 234 isclosed from the base unit 232 such that the above described heattransfer functions are achieved within the cartridge 234, whilstavoiding exposure of the remainder of the base unit 232 to therespiratory gas flow. This allows the cartridge 234 to be provided as areplaceable, and typically disposable, component, which can be removedfrom the base unit 232 after use. The base unit 232 can thus be reusedby attaching a new cartridge thereto in the manner described above.

The condensate within the condensing portion of the cartridge interiorgathers on the internal walls and runs down to the base wall 239 of thecartridge under the action of gravity. Accordingly, a condensatecollection arrangement is provided which communicates with the cartridgevia the port connector 236 shown in FIG. 17. This condensate collectionarrangement may have either of the forms described above, with referenceto FIGS. 13 and 14.

The second embodiment of the apparatus, which is described above, wouldbe constructed with the base unit 232 being housed within a casing (notshown in the Figures). The casing would include an arrangement forreleasably engaging the cartridge 234. In particular, the projections270,274 of the conductor arrangement would be exposed, such that thecartridge 234 may be replaceably engaged with those projections 270,274.The casing would also include flow outlets for the air emitted by thefan 258 to exit the apparatus.

FIG. 21 shows a third embodiment of dehumidification apparatus accordingto the invention, which is generally designated 326. The apparatus 326is similar to the second embodiment described above. However, in thisembodiment, the base unit 332 is shown with a casing, which houses anarrangement that is almost identical to the base unit 232 describedabove in relation to the second embodiment 226, and hence including aheat exchange device (Peltier device), an associated conductorarrangement, a fan unit and an associated heat sink.

The principal difference between the base unit 332 of the thirdembodiment and that of the second embodiment is that the base unit 332is provided with a number of projections 374 that are in communicationwith the hot side of the heat exchange device (Peltier device) that isequal to the number of projections 370 that are in communication withthe cold side of the heat exchange device (Peltier device). Theseprojections 370,374 are visible in FIG. 22.

As shown in FIG. 22, the base unit 332 includes a generally rectangularrecess 333, of substantially uniform depth, in its upper wall forreceiving the cartridge 334. The two sets of projections 370,374 thatare in communication with the heat exchange device (Peltier device)370,374 project from respective openings in the floor of the recess 333,such that these projections 370,374 are upstanding within the recess333. The recess 333 is arranged at an oblique angle relative to thesurface on which the base unit 332 rests, such that the cartridge 334 isarranged at an oblique angle relative to horizontal, in use, and waterdrains down to the liquid drainage port 336.

The base unit 332 also includes a series of parallel, rectangularopenings on its front wall, which serve as outlets for the airflowgenerated by the fan of the base unit 332.

As shown in FIGS. 23 and 24, the cartridge 334 is formed of twoinjection moulded components, which define a flow chamber extendingbetween an inlet port 328 and an outlet port 330. The inlet and outletport 328 and 330 extend parallel to each other, from one end of an uppersurface of the cartridge 334, such that these ports project upwardlyfrom the apparatus 326 when the cartridge 334 is engaged with the baseunit 332. At the other end of the cartridge 334, a liquid drainage port336 extends in the opposite direction to the inlet and outlet ports328,330, such that the liquid drainage port 336 extends downwardly atone end of the base unit 332, when the when the cartridge 334 is engagedwith the base unit 332.

The lower wall of the cartridge, which is visible in FIG. 24, is formedwith a plurality of parallel recesses 346, which in turn causes the flowchamber to include a plurality of respective projections. These recesses346 correspond in number, namely eight, and to the number of projections370,374 in the recess 333 in the upper wall of the base unit 332, andhave a corresponding form, such that these recesses 346 receive theprojections 370,374, with a close fit, when the cartridge is engagedwith the recess 333. In particular, the exterior surface of the lowerwall of the cartridge 334 having these recesses 346 is in contact withthe external surface of the projections 370,374 of the base unit 332 toenable effective heat transfer between the cartridge 334 and the baseunit 332.

As discussed above, the two sets of projections 370,374 that are incommunication with the heat exchange device (Peltier device) 370,374project from respective openings in the floor of the recess 333, andcontact the lower wall of the cartridge 334. Each set of projections370,374 consists of four parallel projections 370,374, which engage withrespective halves of the lower wall of the cartridge 334. In particular,the projections 370 that are in communication with the cold side of theheat exchange device (Peltier device) are in contact with the half ofthe cartridge 334 into which the inlet port 328 extends, and theprojections 374 that are in communication with the hot side of the heatexchange device (Peltier device) are in contact with the half of thecartridge 334 into which the outlet port 330 extends. In thisarrangement, as in the arrangement of the first embodiment, therespiratory gases entering the cartridge through the inlet port 328 arefirstly cooled by heat transfer to the ‘cold’ set of projections 370,through the lower wall of the cartridge 334, thereby causing water tocondense and flow down to the liquid drainage port. The respiratorygases then pass into the other half of the cartridge 334, and are heatedby heat transfer from the ‘hot’ set of projections 370, through thelower wall of the cartridge 334, such that water no longer condenses.The respiratory gases then exit the cartridge 334 through the outlet330.

1. (canceled)
 2. Apparatus for condensing water from respiratory gases,comprising a heat exchange component having an inlet, an outlet and acondensation chamber, the inlet and outlet being connectable to abreathing system, such that respiratory gases are conveyed through thecondensation chamber, in use, and a base unit adapted to aid removal ofheat from the walls of the heat exchange component, wherein the heatexchange component is releasably engageable with the base unit, suchthat the heat exchange component is replaceable, wherein the heatexchange component forms a closed system relative to the base unit, suchthat there is no contact between the base unit and the respiratorygases, and wherein the heat exchange component includes a watercondensate outlet port, which is adapted to enable the removal of watercondensate from the heat exchange component.
 3. The apparatus of claim2, wherein the water condensate outlet port allows the flow of watercondensate out of the heat exchange component, without allowing the flowof respiratory gases through the port.
 4. The apparatus of claim 2,wherein the water condensate outlet port, or a fluid conduit connectedthereto, includes a duckbill valve.
 5. The apparatus of claim 2, whereinthe apparatus includes a sump component that is removably connected tothe water condensate outlet port of the heat exchange component.
 6. Theapparatus of claim 5, wherein the apparatus includes a valve for closingthe water condensate outlet port when the sump component is removed foremptying or disposal.
 7. The apparatus of claim 6, wherein the valveincludes one or more duckbill valves, which are maintained in an openconfiguration by the presence of the sump component in connection withthe heat exchange component, and which revert to a closed configurationwhen the sump component is disconnected from the heat exchangecomponent.
 8. The apparatus of claim 7, wherein the sump component isadapted to cause the movement of resiliently movable, outwardlyextending arms of the valve on connection of the sump component to theheat exchange component.
 9. The apparatus of claim 7, wherein the valveincludes two duckbill valves, which are coupled by a connection member,such that connection of the sump component to the heat exchangecomponent causes both duckbill valves to open.
 10. The apparatus ofclaim 2, wherein the water condensate outlet port includes a floatvalve, which prevents the flow of water condensate out of the heatexchange component when the level of water condensate within the heatexchange component is below a threshold level and allows the flow ofwater condensate out of the heat exchange component when the level ofwater condensate within the heat exchange component is at or above athreshold level.
 11. The apparatus of claim 2, wherein the heat exchangecomponent is a disposable component.
 12. The apparatus of claim 2,wherein the heat exchange component is formed of plastics material. 13.A heat exchange component for condensing water from respiratory gasesand having an inlet, an outlet and a condensation chamber, the inlet andoutlet being connectable to a breathing system, such that respiratorygases are conveyed through the condensation chamber, in use, wherein theheat exchange component is releasably engageable with a base unitadapted to aid removal of heat from the walls of the heat exchangecomponent, wherein the heat exchange component forms, in use, a closedsystem relative to said base unit, such that there is no contact betweenthe base unit and the respiratory gases, and wherein the heat exchangecomponent includes a water condensate outlet port, which is adapted toenable the removal of water condensate from the heat exchange component.14. The heat exchange component of claim 13, for use in an apparatus forcondensing water from respiratory gases, comprising a heat exchangecomponent having an inlet, an outlet and a condensation chamber, theinlet and outlet being connectable to a breathing system, such thatrespiratory gases are conveyed through the condensation chamber, in use,and a base unit adapted to aid removal of heat from the walls of theheat exchange component, wherein the heat exchange component isreleasably engageable with the base unit, such that the heat exchangecomponent is replaceable, wherein the heat exchange component forms aclosed system relative to the base unit, such that there is no contactbetween the base unit and the respiratory gases, and wherein the heatexchange component includes a water condensate outlet port, which isadapted to enable the removal of water condensate from the heat exchangecomponent.
 15. A breathing system comprising the apparatus of claim 2.16. A breathing system comprising the heat exchange component of claim13.
 17. The breathing system of claim 16, wherein the breathing systemis a breathing circuit comprising a ventilator or an anesthetic machine,an inspiratory limb, and an expiratory limb.
 18. The breathing system ofclaim 17, wherein an apparatus for condensing water from respiratorygases, comprising a heat exchange component having an inlet, an outletand a condensation chamber, the inlet and outlet being connectable to abreathing system, such that respiratory gases are conveyed through thecondensation chamber, in use, and a base unit adapted to aid removal ofheat from the walls of the heat exchange component, wherein the heatexchange component is releasably engageable with the base unit, suchthat the heat exchange component is replaceable, wherein the heatexchange component forms a closed system relative to the base unit, suchthat there is no contact between the base unit and the respiratorygases, and wherein the heat exchange component includes a watercondensate outlet port, which is adapted to enable the removal of watercondensate from the heat exchange component, is connected within thebreathing circuit, such that it forms part of the expiratory limb.